“And utter a parable to the rebellious house, and say to them, ‘Thus says the Lord Yahweh, set on the cauldron, set it on, and also pour water into it. Gather its pieces into it, even every good piece, the thigh and the shoulder. Fill it with the choice bones. Take the choice of the flock, and pile also the bones under it. Make it boil well. Yes, let its bones be seethed in the midst of it.' ”
The idea of the cauldron has already been used by Ezekiel (Ezekiel 11:1-13). (Compare Jeremiah 1:13). There we learned that the city of Jerusalem was the cauldron and its people the flesh within.
So the setting on of the cauldron with the stew being cooked within it was his way of indicating to his hearers that the final events were taking place. All the ‘choice' people were gathered into it and the pot had begun to boil.
Note the continued use of ‘rebellious house' for Ezekiel's hearers. It was not only Jerusalem that was in rebellion against God but almost the whole house of Israel. If they did not hear and repent they would share the fate of Jerusalem.